Higher sync but lower download speeds

[#1]

Hi
I wonder if anyone could help with this...
I am just over 10 days into my new adsl connection, and this morning rebooted my router.  Throughout the first 10 days I was connected at 5947 kbps with an ip profile of 5.25Mbps according to the BT speedtest, and a line speed of 5.2Mb according to the PlusNet member centre. During these 10 days I was getting consistent download speeds of around 5.25Mbps.
After rebooting my router this morning, I am connected at 6355 kbps, and on the BT speedtest site my ip profile is now 5.61 Mbps - but my download speed is now lower at around 4.9Mbps. PlusNet are still reporting my line speed as 5.2Mb.
Can anyone explain why my download speed has dropped, and even better, let me know how to get it back up again?? 
Speedtest results and router stats for before and after the reboot below:
Thanks
Alan

BT Speedtest results from 19th September:
1. Best Effort Test:  -provides background information.
Download  Speed  5.27 Mbps

      Max Achievable Speed    7.15 Mbps

Download speed achieved during the test was - 5.27 Mbps
For your connection, the acceptable range of speeds  is 2 Mbps-7.15 Mbps.
IP Profile for your line is - 5.25 Mbps
2. Upstream Test:  -provides background information.
Upload Speed  0.34 Mbps

Max Achievable Speed 0.45 Mbps
Upload speed  achieved during the test was - 0.34Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.45 Mbps
Router stats:
Uptime: 9 days, 22:52:51
DSL Type: ITU-T G.992.3
Bandwidth (Up/Down) [kbps/kbps]: 443 / 5.947
Data Transferred (Sent/Received) [GB/MB]: 1,99 / 268,67
Output Power (Up/Down) [dBm]: 12,7 / 0,0
Line Attenuation (Up/Down) [dB]: 26,0 / 42,0
SN Margin (Up/Down) [dB]: 20,8 / 6,2
System Vendor ID (Local/Remote): TMMB / ----
Chipset Vendor ID (Local/Remote): BDCM / IFTN
Loss of Framing (Local/Remote): 16 / 0
Loss of Signal (Local/Remote): 2 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): -
Error Seconds (Local/Remote): 4.211 / 0
FEC Errors (Up/Down): 0 / 0
CRC Errors (Up/Down): 85 / 4.900
HEC Errors (Up/Down): 39 / 10.334

And from today:
1. Best Effort Test:  -provides background information.
Download  Speed  4.91 Mbps

Max Achievable Speed  7.15 Mbps

Download speed achieved during the test was - 4.91 Mbps
For your connection, the acceptable range of speeds  is 2 Mbps-7.15 Mbps.
IP Profile for your line is - 5.61 Mbps
2. Upstream Test:  -provides background information.
Upload Speed  0.34 Mbps

Max Achievable Speed  0.45 Mbps
Upload speed  achieved during the test was - 0.34Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.45 Mbps
Router stats:
DSL Type: ITU-T G.992.3
Bandwidth (Up/Down) [kbps/kbps]: 443 / 6.355
Data Transferred (Sent/Received) [MB/MB]: 25,01 / 372,26
Output Power (Up/Down) [dBm]: 12,8 / 0,0
Line Attenuation (Up/Down) [dB]: 25,9 / 42,0
SN Margin (Up/Down) [dB]: 22,2 / 6,1
System Vendor ID (Local/Remote): TMMB / ----
Chipset Vendor ID (Local/Remote): BDCM / IFTN
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 0 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): -
Error Seconds (Local/Remote): 101 / 0
FEC Errors (Up/Down): 0 / 0
CRC Errors (Up/Down): 25 / 115
HEC Errors (Up/Down): 14 / 242

[#2]

Hi there,
Just bumped your profile on our side up to 5600kbps to match the BT profile, hope that improves things for you.

[#3]

Thanks Matt
Am now getting 5.32 on BT Speedtest - so much better, although still not as high as I had hoped on a sync of 6355.  But then again, maybe I was being over-optimistic!

[#4]

Your profile on 21CN is always 88.2% of the sync rate, or it certainly should be. The profile of 5600 is correct in that case - (6355/100)*88.2 = 5605.
You'll not see the full speed of the profile though due to packet headers and overheads etc, hence the throughput of around 5.3Mb.
Hope that helps explain.